Generalized TriangleBenchmark to support rendering a triangle of a solid color (hard-coded in shader), interpolated input colors, and interpolated colors with texture sampling. Added benchmark captures for each type, along with multi-sampled versions of each. Bug: b/176981107 Change-Id: Iadef1f0f9a339038198f8ef0e492c4c2909a96b2 Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/51889Tested-by: Antonio Maiorano <amaiorano@google.com> Commit-Queue: Antonio Maiorano <amaiorano@google.com> Reviewed-by: Nicolas Capens <nicolascapens@google.com> Kokoro-Result: kokoro <noreply+kokoro@google.com>